Euphausia superba krill are the most common krill, found mostly in the waters of the Antarctic. Euphausia krill are at the very bottom of the food chain and can only found in the pristine oceans around Antarctcia, where there is very limited accumulation of contaminants.

How many different species of krill are they?

There are 85 known species of krill. Krill is comprised of two families the largest of which is Euphausiidae which contains 20 different genra, the largest of which is the Euphausia. The other family of Krill is the Bentheuphausia ampblyops, which lives in the deep waters (below 3,330 feet) and are the most primitive species of krill.

The most well known species of the Euphausiidae are the Antarctic Krill (Euphausia superba), Pacific krill (Euphausia pacifica) and Northern krill (Meganyctiphanes norvegica).

Actual Size: 2½ inches (or your pinky finger)

Description

With large black eyes, krill are mostly transparent, although their shells have a bright red tinge. Their digestive system is usually visible. Krill have a hard exoskeleton, many legs which they use to swim and eat, and a segmented body.

Population

Antarctic krill are one of the most abundant animal species, there are about 500 million tons of krill in the Southern Ocean.

Krill travel in swarms primarily as a defense mechanism to confuse predators that would pick out single krill. In additional efforts to avoid predators, krill are found to spend their day at greater depths in the ocean and rise during the night toward the surface. It has also been found that the deeper they go in the water, the more their activity lessens, to reduce the probability of encounters with predators as well as conserve their energy.

Lifespan

The lifespan of a krill is typically up to 10 years, six years on average which is not bad for a heavily sought after creature.

Life Cycle: The main spawning season of Antarctic Krill is from January to March, above the continental shelf. Female krill lay up to 10,000 eggs at a time, sometimes several times a season.

The eggs are spawned close to the surface and start sinking. In the open ocean they sink for about 10 days: the nauplii hatch at around 3000 m depth.

What do they eat?

A close-up of phytoplankton.

Antarctic Krill are mainly herbivorous (they sometimes eat each other), feeding mostly on phytoplankton (microscopic suspended plants). They feed directly on phytoplankton, thereby using the primary production energy that phytoplankton derive from the sun in order to sustain their open ocean life cycle. Some krill also eat zooplankton

In winter they have to use other sources such as algae which grow on the underside of the ice, on the sea-floor. Krill can survive for long periods of time without food (up to 200 days) and can shrink in length as they starve.

How big are they?

They grow to a length of 2½ inches (6 centimeters), and weigh up to .07 ounces (2 grams).